The experiments prove that a virus may become inert in practice; this avirulency is due to some foreign matter, inasmuch as inert virus added to virulent sterile virus promptly produces avirulency. It is probable that this avirulency is due to the presence of some germ, but the experiments have not been carried out to the extent necessary to determine the nature of this micro-organism.
1. The avirulency of a virus takes place a certain time after mixing sterile to inert virus.
2. The avirulency takes place more rapidly when the mixture is kept in the incubator than when it is kept at room temperature.
3. The mixture of virulent and inert virus produces different results in injected animals according' 1"0 the method of inoculation. The same virus which proves inert after a subcutaneous injection may be virulent for an intrajugular injection.
4. The intrajugular injection of large doses of inert virus does not produce immunity.
5. It is clear that a certain virus may become inert, and therefore this fact influences the preparation and preservation of virus to be used in practice.
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